Spline-type cam phaser

Abstract

An improved splined cam phaser includes four assemblies: a sprocket assembly, an inner hub assembly, a cover assembly, and a piston assembly. The joined assemblies provide phaser function at reduced manufacturing cost. The component parts of the assemblies are re-configured from analogous parts in the prior art cam phaser to permit much of the improved phaser to be manufactured inexpensively by powdered metal forming or by stamping or drawing from sheet metal, in contrast with the prior art phaser wherein all parts are formed expensively either by machining from forged blanks or by investment casting. These changes reduce not only the cost of manufacture but also reduce the weight and axial length of the phaser, an important customer acceptance criterion, and improve the speed of response. Further, the proportions of some parts are altered such that all radial and axial loads are borne by a single large bearing in place of two small sequential bearings in the prior art phaser, thus reducing variability in axial alignment of the component parts.

What is claimed is:  
     
       1. A variable cam phaser for attachment to a camshaft of an internal combustion engine for varying the phase relationship between the camshaft and a crankshaft by application of variable force to the phaser, comprising: 
       a) input drive means for receiving input rotary motion from said crankshaft and for transmitting said input rotary motion to said camshaft;  
       b) sprocket flange means adjustably mounted to said input drive means and rotatable therewith and having first-handed internal helical splines on a portion of a radial inner surface thereof distal from said camshaft;  
       c) inner hub flange means connectable to said camshaft for transmitting the rotary motion from said input drive means to the camshaft, said inner hub flange means having a hub portion and a flange portion disposed within said sprocket flange means, said flange portion extending axially over a portion of said radial inner surface of said sprocket flange means proximal to said camshaft to define an axially extensive bearing therebetween, said inner hub flange means having second-handed external helical splines extending into a first annular space opposite said first-handed internal helical splines on said sprocket flange means;  
       d) outer hub means coupled to said inner hub flange means to define a second annular space between said outer hub means and said hub portion of said inner hub flange means and further a third annular space between said outer hub means and the distal portion of said sprocket flange means;  
       e) annular piston means disposed within said second annular space and dividing said space into a first compression chamber distal from said camshaft and a second compression chamber proximal to said camshaft, said annular piston means having external helical splines in meshable relationship with said splines on said sprocket flange means and having internal helical splines in meshable relationship with said splines on said inner hub means, said piston means being operable upon application of fluid pressure in one of said first and second compression chambers to move in a direction toward the other of said chambers to act on the splines and thereby radially displace said inner hub flange means and said sprocket flange means with respect to each other to adjust the phase between the crankshaft and the camshaft; and  
       f) a cover assembly including cover means sealably mounted to an outer end of said sprocket flange means and to an outer surface of said outer hub means to enclose said first compression chamber, said cover means having a central opening therethrough for receiving said outer hub means and being connected to said outer hub means for rotation therewith.  
     
     
       2. A variable cam phaser in accordance with  claim 1 , wherein said input drive means is selected from the group consisting of sprocket wheel, gear, and pulley. 
     
     
       3. A variable cam phaser in accordance with  claim 1 , wherein at least one of said sprocket flange means, said inner hub flange means, and said annular piston means is formed by machining from a forged blank, and wherein at least one of said input drive means, said outer hub means, and said cover means is formed by a process other than by machining from a forged blank. 
     
     
       4. A variable cam phaser in accordance with  claim 1 , further comprising a timing wheel disposed coaxially on said outer hub means. 
     
     
       5. A variable cam phaser in accordance with  claim 1 , wherein said annular piston means includes an annular phase control piston and an annular lash control piston. 
     
     
       6. A variable cam phaser in accordance with  claim 1 , wherein said inner hub flange means is formed by powdered metal forming and wherein said inner hub flange includes oil passages net shaped in said forming. 
     
     
       7. A variable cam phaser in accordance with  claim 1 , wherein said inner hub flange means further includes a pressed-on ring for retaining a piston seal for forming a seal against said annular piston means.